Identify this lesion in the formation of Atherosclerosis.
A. Early lesion
B. Fully developed Atheromatous Plaque
C. Complicated Plaque
D. None of the above.
Ans:C. Complicated Plaque
Schematic Evolution of Lesions in Atherosclerosis.
1. FATTY STREAKS AND DOTS.
- Grossly, the lesions may appear as flat or slightly elevated and yellow.
- They may be either in the form of small, multiple dots, about 1 mm in size, or in the form of elongated, beaded streaks.
- Microscopically, fatty streaks lying under the endothelium are composed of closely-packed foam cells, lipid containing elongated smooth muscle cells and a few lymphoid cells.
2. GELATINOUS LESIONS.
- They are round or oval, circumscribed grey elevations, about 1 cm in diameter.
- Microscopically, gelatinous lesions are foci of increased ground substance in the intima with thinned overlying endothelium.
3. ATHEROMATOUS PLAQUES.
- A fully developed atherosclerotic lesion is called atheromatous plaque, also called fibrous plaque, fibrofatty plaque or atheroma.
- Grossly, atheromatous plaques are white to yellowish white lesions, varying in diameter from 1-2 cm and raised on the surface by a few millimetres to a centimetre in thickness.
- Cut section of the plaque reveals the luminal surface as a firm, white fibrous cap and a central core composed of yellow to yellow-white, soft, porridgelike material.
- Microscopically, the following features are invariably present :
- Superficial luminal part of the fibrous cap is covered by endothelium, and is composed of smooth muscle cells, dense connective tissue and extracellular matrix containing proteoglycans and collagen.
- Cellular area under the fibrous cap is comprised by a mixture of macrophages, foam cells, lymphocytes and a few smooth muscle cells which may contain lipid.
- Deeper central soft core consists of extracellular lipid material, cholesterol clefts, fibrin, necrotic debris and lipid laden foam cells.
4. COMPLICATED PLAQUES.
- Various pathologic changes that occur in fully-developed atheromatous plaques are called the complicated lesions.
- These changes include calcification, ulceration, thrombosis, haemorrhage and aneurysmal dilatation.